Dental casting device



Aug. 10,1926.

C. S. BRAZDA ET AL DENTAL CASTING DEVICE Filed June 8, 1925 2 Sheets-Shoot 1 Aug. 10 1926.

i c. s. BRAZDA ET AL DENTAL CASTING DEVICE Filed June 8 1925 2 Sheets-Sheet 2 Patented Aug. 10, 1925.

UNITED STATES 1,595,338 PATENT OFFICE.

CTIMIR SILAS BRAZDA, 0F GIGERO, AND LUMIZR.P;AUL BRAZDA, CHICAGO, ILLINOIS.

DENTAL CASTING DEVICE.

Application filed June 8, 1925. 'Serial No. 35,615.

This invention relates to an improvement in sprue supports and crucible formers, resulting in a device which permits the successful casting of a plurality of inlays or dental castings inone casting operation. It has been the practice heretofore to mount a wax pattern of the inlay or other dental casting to be reproduced upon the end of a single metallic sprue mounted centrally and vertically upona crucible former covering, surrounding this crucible former,sprue, and pattern with a metallic ring known as a flask, then filling the flask to the upper level with a pastyinvestment compound which later sets. The crucible former was then removed, leaving a smooth crucible from the base of which a portion of the metallic sprue former extended. This sprue former could then be removed with pliers, leaving a small cylindrical hole extending into the wax pattern. Upon the application of heat the wax pattern was melted out, the wax being either absorbed by the plaster or passing out through the sprue hole in the form of molten wax or vapor.

In accordance with our invention, we provide means for supporting a plurality of such sprue formers and wax patterns on a single crucible former, without interfering with the removal of the crucible former. In order to accomplish this result, the crucible former is made in a plurality of parts, so that a portion of it may be first removed, after which all of the angularly positioned sprue formers may be removed, and finally the remaining portion of the crucible former and a centrally located sprue former are removed.

Our invention is illustrated in the accompanying drawings, in which- Figure 1 is a plan view of the crucible former, with its central portion removed;

Figure 2 is a plan view of the removed central portion of the crucible former;

Figure 3 is an elevation ofthe removed and central portion of the crucible former;

Figure 4: is an elevation of the crucible former, a part of which is shown in section;

former, into which has been assembled seven sprue formers, upon which are mounted seven wax patterns to be cast;

'Figure 6 is a section through av .flask, into which investment compound has been poured;

Figure 5 is a perspective of the crucible Figure 7 represents a section through the same flask after the external part of the crucible former has been removed;

Figure 8 is a section through the same flask afterthe external part of the crucible former andthe-outer series of sprue formers have been removed;

Figure9 is a section through a flask after the entire crucible former and the outer series of sprue formers have been removed;

Figure 10 .is a section through a flask, from which the crucible former and sprue former have been removed; and I Figure 11 is a section through a flask, showing the molten globule of metal about to be forced into the molds.

By reference to Figures 1 to 4, inclusive, it may be seen that the outer portion of the crucible former 12 comprises a member hav ing a circumferential shoulder 13, upon which a flask 14 (Figs. 6 to 10) may be placed, the cylindrical portion 15 of thecrucible former being adapted .to extend slightly into the flask for the purpose of properly centering the crucible former. The part 16 of the crucible former coming in contact with the investment compound is of a general conical shape, and is provided near the apex with a central conical-cavity, into which the part 1890f the-crucible former shown in Figs. 2 and 3, and constituting a central portion of the crucible former, is fitted. The external part 16 of the crucible former is provided with a plurality of sprue receptacles, in the form of U-.

shaped grooves 20, in the wall of the inner conical cavity, and extending parallel with theconical face of this inner cavity. When the part '18 is assembled within the part 12, to complete thecrucible former, the grooves 20 are closed along their open sides by the part 18, and thus form a plurality of U- shaped holes orpockets, into which a plurality of sprues 21, as shown in Fig. '5, may be stood. The central portion of the member 18 is preferably provided with an opening 22 for the reception of a central sprue 23 (Fig. 5), and is also provided with a projection 24;, by means of which the part 18 maybe grasped with pliers, to free it from the investment, as will be later described.

' In carrying out the process of preparing a mold for the casting of a plurality of inlays or other-dentures, the parts are-assembled as shown in Fig. '5, each sprue former carrying on its projecting end a. wax pattern of the part to be reproduced in gold or any other dental metal. The flask 14' is then placed over the crucible former 16, and the investment compound represented at 25 is poured in until the flask is substantially completely filled. After the compound has been allowed to set and harden, the flask is turned over and the outer portion 16 of the crucible former removed.

As shown in Fig. 7, when the device is in this condition, the ends of the sprue formers 21 may be grasped with pliers, and the sprue formers may thus be pulled out of the investment compound by a pressure directed axially of each individual sprue former. hen all of the sprue formers located about the circumference of the inner conical men ber 18 have been removed, as shown in Fig. 8, the inner member 18 may be grasped with pliers and removed, leaving the flask as shown in Fig. 9, with only the central sprue former in place, which may then be removed with pliers, leaving the flask with its invested wax patterns, as shown in Fig. 10. After the wax has been driven ofl by heat, a mass of gold or other dental metal will be melted in the crucible, as shown in F ig. 11, and the metal or metallic composition simultaneously driven into all of the cavities by the application of air, steam pressure, or centrifugal force, or equivalent means, as well known in the art. After the metal has been allowed to chill, the investment may be removed from the flask by the application ofwater, and the nugget of metal, replicas of the sprues and inlays or dental castings extending from it.

The metallic replicas of the sprues are then cut off and the inlays or dental castings separated.

By the use of this device and process de scribed, much time can be saved by the operator, since it is necessary only that one casting be made for a plurality of dental castings, which, according to the present disclosure, may be as many as seven. In case it is desired to cast a number of inlays less than the number for which the crucible former is constructed, it is only necessary to omit sprue formers from some of the receptacles in the crucible former. It is true that investment compound will enter the openings into which no sprue formers have been inserted, but these little columns of compound will be broken off at the level of the base of the crucible by the removal of the part 18 of the crucible former.

It will be understood that although we have shown a crucible former capable of supporting seven sprue formers and patterns at one time, a less or greater number of receptacles for sprues may be provided, the principal limitation being the number of inlays which can be spaced within the particular flask to be used. The lnside diameter of a standard flask is about one and one-eighth inches, and we have found in practice that seven inlays may be readily cast, using this standard size flask, and that the walls of investment between the inlays will not break down, even though the patterns come very close to'one another, so long as they do not actually touch.

'l Vhat we claim is:

1. A crucible former and sprue former support, comprising a member of general conical shape, adapted to form the walls of the crucible, a central member adapted to form the base of the crucible, the outer and inner portions being separable and provided with receptacles for sprue formers at the separation surfaces, the slope of the wall between the inner and outer portions of the crucible former being such as to provide an increasing clearance between the inner and outer portions as the two portions are separated.

2. A crucible former and support for holding a plurality of sprue formers in angular relation to one another, comprising two members, one having a plurality of receptacles formed therein for receiving the ends of the sprue formers, the other member constituting a part of the crucible former and adapted to lit Within a central depression in the main body of the first former and to form a wall of each of said receptacles.

3. A dental casting device including a crucible former provided with a plurality of radiating sprue former receptacles, said crucible former being formed of two parts, each of which constitutes a wall of each of said receptacles, the slope of the walls between the tWo parts of said crucible former being such as to substantially follow the slope of the axis of said sprue former receptacles at each receptacle, whereby the outer part of the crucible former may be freely removed after investment has been poured adjacent it and around said sprue formers, by the separation of the two parts of the crucible former, and whereby the ends of the sprue formers, are thus exposed for axial removal of each sprue former from the investment, and whereby the inner part of the crucible former may be removed from the investment after the sprue formers have been removed.

4. A dental casting device, including a crucible former formed of a plurality of parts, each part having a surface constituting a part of the crucible former surface coming adjacent investment compound, a plurality of radially disposed sprue formers projecting from said crucible former and adapted to be surrounded by investment compound in the use of the device, the slope of the faces between the parts of the crucible former being such as to permit the separation of the parts of the crucible former by relative movement along the axis of the crucible former, the separation permitting the removal of the other part or parts of the crucible former and the said radially positioned sprue formers from the investment compound.

5. A casting device for dental castin s and the like, comprising a two part crucible former, the inner and outer parts each having a surface coming in contact with the investment compound when the device is used, the inner part being generally conical in shape, the apex portion extending into the outer member of the crucible former, a part of the conical wall being cut away to form a part which may be readily gripped, for removing the inner portion from the investment compound after the outer portion has been removed therefrom.

6. A casting device for dental castings and the like, including a two part crucible former, the inner part being of substantially conical shape, with its apex extending into the outer part, and each part having a surface coming adjacent the investment compound when the casting device is in use, the outer part having formed therein a plurality of radially disposed sprue former receptacles, all of substantially equal depth, one

wall of each of said receptacles being closed by the adjacent wall of the conical part of said crucible former, and a plurality of sprue formers positioned within said receptacles and extending radially with their axes parallel to the adjacent wall of the conical part of the crucible former, whereby when the parts of the crucible former are assembled together, separate sprue formers may be inserted one at a time in said receptacles, and whereby after investment compound has been poured adjacent the parts of said crucible formers and around said sprue formers, the removal of the outer portion of the crucible former will leave the inner portion of the crucible former retained in position adjacent the investment compound by the protruding ends of the radiallydisposed sprue formers,

and whereby said sprue formers are thus exposed for axial withdrawal from the investment compound, thus releasingthe conical portion of the crucible former, so that it may be removed from the investment compound.

In witness whereof, we hereunto subscribe our names this 25th day of May, 1925.

GTIMIR SILAS BRAZDA. LUMIR PAUL BRAZDA. 

